1. Field of the Invention
The present invention relates to an image projection apparatus and a white balance adjustment method thereof. More particularly, the present invention relates to an image projection apparatus which uses a light emitting diode as a light source and a white balance adjustment method thereof.
2. Description of the Related Art
An image projection apparatus receives an image signal, forms an image corresponding to the image signal, and projects the image on a screen. Such an image projection apparatus is called a “projector.” The image projection apparatus typically adopts the following image forming process. White light emitted from a white lamp passes through a color wheel. The color wheel filters the white light into red (R)-light, green (G)-light and blue (B)-light in sequence. The R, G, and B-lights are modulated into a corresponding image by a digital micromirror device (DMD).
However, the white lamp has disadvantages of large bulk and high power consumption. Therefore, if the image projection apparatus uses the white lamp as a light source, the volume of the image projection apparatus becomes increased and power consumption is increased. This is more problematic if the white lamp is used as a light source in a portable image projection apparatus to be carried with a battery for power supply.
In order to solve this problem, an image projection apparatus using three color (red, green, blue) light emitting diodes (LEDs) as a light source has been suggested.
However, when the LEDs are driven for a long time, temperatures of the LEDs increase, which causes a reduction in levels of lights emitted from the LEDs. The degree of reduction of light level caused by the increase of temperature differs depending on the kind of LEDs and manufacturers of the LEDs. Accordingly, when the image projection apparatus using the LEDs as a light source is in use for a long time, deviations with respect to the levels of light from the LEDs become unacceptable. As a result, deviations with respect to amounts of R-light, G-light, and B-light become unacceptable.
The unacceptable deviations of the light amounts cause image degradation of the image provided to a user, and also require a white balance to be adjusted. Accordingly, there is a need for an improved image projection apparatus that is capable of adjusting a white balance in consideration of a level of light emitted from an LED and a corresponding method thereof.